This invention relates to flushable body waste collection pouches, and particularly to a biodegradable pouch suitable for use as the toilet-disposable inner pouch of a pouch-within-a-pouch ostomy appliance of the type generally disclosed in U.S. Pat. No. 5,865,819. The disposable pouch has a pair of walls secured together along their peripheral edges to define a waste-receiving chamber, and one of the side walls has a body waste receiving opening which communicates with that chamber. External attachment means are provided about the opening for attachment of the pouch (or pouch assembly) to a wearer.
The only inner pouch currently on the market is a pouch available from Welland Medical covered by U.S. Pat. No. 5,938,647. This pouch is made of hot water soluble polyvinylalcohol. The problem with polyvinylalcohol is that it becomes brittle and noisy upon aging and has limited biodegradability. Thus, there is a need for an inner pouch file that is flexible, water impermeable, has low noise (an important requirement for ostomy and fecal incontinence pouches) and good biodegradability.
The walls of a pouch embodying this invention are composed of a thin, heat sealable (including RF sealable) and liquid-impermeable monolayer film of a composition comprising a plasticized biodegradable aliphatic polyester, or a plasticized biodegradable aliphatic-aromatic copolyester, or blends thereof, covered by a water-disintegratable layer of biodegradable and water-dispersible fibers, most preferably cellulosic fibers, bonded thereto. The polyester or copolyester is blended with an aliphatic ester plasticizer such as triethylcitrate or vegetable oil. Such a plasticizer imparts greater flexibility to the film, reduces film noise upon wrinkling, and allows extrusion of the resin into films or coatings as thin as 10 microns (0.8 mil) or less. It has also been found that the presence of the plasticizer effectively increases the rate of biodegradation of the film. Starch may also be used advantageously as a biodegradable plasticizer.
The composition of the film may comprise a blend of about 70% to 95% by weight of the biodegradable aliphatic polyester or aliphatic-aromatic copolyester and 5% to 30% of a biodegradable plasticizer or plasticizers. More desireably, the blend is within the range of about 75% to 93% polyester or copolyester and about 7% to 25% plasticizer(s). A preferred composition is believed to be about 90% polyester or copolyester and about 10% plasticizer(s).
The aliphatic polyester may comprise a polymer made by ring-opening polymerization of a lactone, preferably polycaprolactone. The aliphatic-aromatic copolymer may comprise a condensation product of a glycol with a combination of an aliphatic diacid and aromatic diacid, wherein the aromatic diacid is less than 20% by mole.
To enhance biodegrability, minimize noise, and reduce cost, the film should be ultra-thin, having a thickness no greater than about 40 microns (1.57 mil). A preferred thickness range is believed to be about 6 to 40 microns (0.24 to 1.57 mil) with a more preferred range being about 10 to 35 microns (0.39 to 1.38 mil). Particularly effective results are believed to occur when the thickness range is about 15 to 30 microns (0.59 to 1.18 mil).
The ultra-thin monolayer film, having the advantages and features described above, is reinforced by the water-disintegratable cover layer defining the outer surfaces of the pouch. The cover layer is composed of a random arrangement of water-dispersible fibers, has no non-water-soluble binder (and preferably no binder at all) and has significant dry strength with virtually no elongation but lacks wet strength. Tissue paper having a high cellulosic fiber content, preferably 100%, is believed particularly effective The monolayer film may be secured uninterruptedly throughout one of its side surfaces to the tissue or other reinforcing substrate by any suitable means. While adhesive attachment (as by a water-soluble and biodegradable adhesive) is considered feasible, it is believed more effective to extrude the polyester or copolyester onto the paper substrate to form a thin but uninterrupted coating thereon or to laminate the two layers together with heat, with the attachment between the opposing surfaces of the two layers in either case being produced with heat and being mechanical in nature. As long as the external surface of the pouch is in a dry state, the tissue paper covering offers mechanical strength, softness, and noise reduction but, upon exposure to water, as when the pouch is discarded into a flush toilet, the tissue disintegrates rapidly and is believed to contribute to flushability by rapidly absorbing water, wetting the film surface, and reducing pouch buoyancy.
An important aspect of this invention lies in the strength, or lack of strength, of the attachment between substantially one entire surface of the cover layer (excluding its peripheral edge portions) and the film that together form each wall of the flushable pouch. (It is along such peripheral edge portions that the layers are securely heat-sealed together to form a completed pouch.) To avoid the formation of unacceptable pinholes in the film, it is essential that none of the fibers of the cover layer extends through the film or even penetrates the film to any appreciable extent. Since the film may be any of a number of different thicknesses, but is ultra-thin in any event, measuring the maximum extent of penetration, if any, is not considered feasible. However, it has been found that no appreciable penetration is achieved, and no pinholes are formed, if the extent of bonding between the paper and film layers is such that the two layers may be peeled away from each other (when dry), with both layers remaining intact, by the application of 180-degree peel forces in the range of about 2 to 10 g/in (0.02 to 0.1 Newtons/in), preferably about 3 to 6 g/in (0.03 to 0.06 Newtons/in). Under such conditions, the layers are found to be bonded together with sufficient strength to maintain the integrity of the pouch wall during use but without risk of unacceptable fiber penetration.
Since the polyester or copolyester films are heat sealable (including RF sealable), the films may be readily converted into pouches using conventional heat sealing methods. Although the film is covered by a soft, flexible and fibrous backing layer as described above, heat sealing is nevertheless readily achieved because the polymeric layers of the pouch walls face inwardly and may therefore be securely welded to each other. Where the pouch serves as the inner pouch of a two-pouch system, it has been found that where the inner pouch has a fibrous and porous cover layer of tissue paper or other suitable fibrous and porous substrate, heat sealing between the film of the inner pouch, the fibrous and porous cover layer, and the film of the outer pouch, as along the peripheral edges of the two pouches, may nevertheless occur. In such a case, the seal between the walls of the outer pouch and the fibrous layer of the inner pouch walls is weaker than the seal between the two walls of the inner pouch, thereby allowing the outer pouch to be torn or peeled away from the inner pouch without adversely affecting the integrity of the inner pouch, at which time the still-intact inner pouch and its contents may be discarded into the water of a toilet bowl to commence the disintegration and biodegradation process.
In such a pouch-in-pouch appliance, where the walls of the flushable inner pouch are composed of thermoplastic film and tissue paper layers weakly bonded together, it is essential that peeling away of the outer pouch not cause delamination of the paper and film layers of the inner pouch since, as already noted, the paper layer is believed to contribute significantly to the flushability of the inner pouch. Also, retention of the soft paper layer by the inner pouch provides tactile benefits for the user who must handle and remove the inner pouch for toilet disposal, as well as assuring the user that the step of peeling away of the outer pouch walls has not compromised the integrity of the inner pouch. An important aspect of this invention therefore lies in avoiding the risks of such delamination by selecting a thermoplastic material for the outer pouch that has a melting temperature greater than that of the thermoplastic material of the inner pouch. Since the fibers of the non-thermoplastic cover layer penetrate the thermoplastic films of both pouches in the zone of the peripheral heat seal, and since the thermoplastic material of the inner pouch has a lower melting temperature, the fiber penetration into the film of the inner pouch along the peripheral heat seal is greater than into the film of the outer pouch and insures that the paper layer will preferentially remain with the inner pouch as the walls of the outer pouch are peeled away.
The peripheral heat seal therefore simultaneously joins the multiple layers together in different ways to achieve peelability of the outer pouch walls away from the fibrous cover layer of the inner pouch, the retention of the fibrous cover layer by the inner pouch, and the true heat-sealing or welding together of the walls of the inner pouch along their peripheral edges.
Other features and advantages of the invention will become apparent as the specification proceeds.